U.S. patent application number 11/827386 was filed with the patent office on 2008-06-19 for self-contained seizure monitor and method.
Invention is credited to Kenneth Shane Guillory, Dimitri Yatsenko.
Application Number | 20080146958 11/827386 |
Document ID | / |
Family ID | 39528360 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080146958 |
Kind Code |
A1 |
Guillory; Kenneth Shane ; et
al. |
June 19, 2008 |
Self-contained seizure monitor and method
Abstract
A self-contained seizure monitor device to monitor a subject for
an electrographic seizure includes a pad with an adhesive layer to
adhere to a subject's skin. At least two electroencephalographic
electrodes are carried by the pad and spaced apart from one another
to sense brain activity and generate a signal. A signal processing
means is carried by the pad and electrically coupled to the
electrodes to process the signal. An indicator is carried by the
pad and electrically coupled to the signal processing means to
indicate seizure information. A power source is carried by the pad
and electrically coupled to the electrodes, the signal processing
means, and the indicator.
Inventors: |
Guillory; Kenneth Shane;
(Salt Lake City, UT) ; Yatsenko; Dimitri; (Salt
Lake City, UT) |
Correspondence
Address: |
THORPE NORTH & WESTERN, LLP.
P.O. Box 1219
SANDY
UT
84091-1219
US
|
Family ID: |
39528360 |
Appl. No.: |
11/827386 |
Filed: |
July 9, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60829148 |
Oct 12, 2006 |
|
|
|
Current U.S.
Class: |
600/544 |
Current CPC
Class: |
A61B 2562/164 20130101;
A61B 5/6814 20130101; A61B 5/369 20210101; A61B 5/4094
20130101 |
Class at
Publication: |
600/544 |
International
Class: |
A61B 5/04 20060101
A61B005/04 |
Goverment Interests
GOVERNMENT LICENSE RIGHTS
[0003] The U.S. Government has a paid-up license in this invention
and the right in limited circumstances to require that the patent
owner to license others on reasonable terms as provided for by the
terms of Grant No. W81XWH-06-C-0021 awarded by the Department of
Defense (Army) SBIR program.
Claims
1. A self-contained device configured to monitor a subject for an
electroencephalographic pathology, the device comprising: a) at
least two electroencephalographic electrodes spaced apart from one
another, and configured to sense brain activity and generate a
signal; b) a signal processing means electrically coupled to the
electrodes for processing the signal; c) an indicator electrically
coupled to the signal processing means and configured to indicate a
physiological condition; d) a power source electrically coupled to
the electrodes, the signal processing means, and the indicator; and
e) means for mounting the device on the subject.
2. A device in accordance with claim 1, wherein the means for
mounting includes a pad with an adhesive layer configured to adhere
to a subject's skin, and wherein the at least two
electroencephalographic electrodes, the signal processing means,
the indicator and the power source are carried by the pad.
3. A device in accordance with claim 2, wherein the pad is flexible
and capable of contouring to a subject's body.
4. A device in accordance with claim 2, wherein the pad includes a
plurality of layers stacked together, including at least: the
adhesive layer, a circuit layer including the signal processing
means and a cover layer.
5. A device in accordance with claim 4, further comprising: at
least two apertures formed in the adhesive layer, and wherein the
at least two electroencephalographic electrodes is at least
partially disposed in the at least two apertures.
6. A device in accordance with claim 1, further comprising: means
for limiting the device to a single use.
7. A device in accordance with claim 2, further comprising: a
release liner removably disposable over the adhesive layer; and a
tab coupled to the release liner and extending between the power
source and an electrical connection.
8. A device in accordance with claim 2, wherein the power source is
sealed within the pad.
9. A device in accordance with claim 1, further comprising at least
one separate electrically coupled electrode capable of being
applied to the subject separately from the at least two
electroencephalographic electrodes.
10. A device in accordance with claim 9, wherein the at least one
separate electrode includes an adhesive layer configured to adhere
to a subject's skin
11. A device in accordance with claim 9, wherein the at least one
separate electrode includes a mechanical clip configured to attach
to the subject.
12. A device in accordance with claim 9, wherein the at least one
separate electrode includes a mechanical compression headband or
hairnet to attach to the subject.
13. A device in accordance with claim 1 further including means for
storing data.
14. A device in accordance with claim 1 further including means for
data transmission.
15. A device in accordance with claim 1, wherein the at least two
electroencephalographic electrodes, the signal processing means,
the indicator and the power source are disposed within the pad.
16. A device in accordance with claim 1, wherein the signal
processing means generates a physiological condition index; and
wherein the signal processing means produces an alarm signal in
response to a change in the physiological condition index.
17. A device in accordance with claim 1, wherein the signal
processing means generates a physiological condition index and the
indicator includes a graphical display to display the physiological
condition index as a time series to indicate change in a
physiological condition over time.
18. An electrographic seizure treatment kit, comprising: a) a
self-contained seizure monitor device configured to monitor a
subject for a seizure, including: i) at least two
electroencephalographic electrodes spaced apart from one another,
and configured to sense brain activity and generate a signal; ii) a
signal processing means electrically coupled to the electrodes for
processing the signal; iii) an indicator electrically coupled to
the signal processing means and configured to indicate seizure
information; and iv) a power source electrically coupled to at
least one of the signal processing means, and the indicator; and v)
means for mounting the device on the subject; and b) a seizure
treatment medication.
19. A kit in accordance with claim 18, further comprising:
instructions for administering the medication to the subject based
on indications from the indicator of the monitor device.
20. A method for monitoring a subject for an electrographic
seizure, comprising: mounting a self-contained seizure monitor
device on the subject, and disposing electroencephalographic
electrodes against skin of the subject; causing the monitor device
to power from a power source of the self-contained monitor device,
and causing the electrodes to sense brain activity and generate a
signal, and causing an EEG signal processor electrically coupled to
the electrodes to process the signal; and perceiving an alarm or a
physiological condition index from an indicator electrically
coupled to the signal processor.
21. A method in accordance with claim 20, wherein mounting further
includes adhering an adhesive layer carried by a pad of the device
to the subject, the pad carrying the electroencephalographic
electrodes, the power source, and the signal processor.
22. A method in accordance with claim 20, further comprising:
removing the monitor device from the subject; and disposing of the
monitoring device.
23. A method in accordance with claim 20, wherein adhering the
adhesive layer carried by the pad further includes positioning
electrodes at least at Fp1 and Fp2 EEG recording locations with the
pad spanning between the electrodes.
24. A method in accordance with claim 20, further comprising:
administering a medication to the subject at least partially based
on indications from the indicator of the monitor device.
Description
PRIORITY CLAIM
[0001] Priority of U.S. Provisional Patent Application Ser. No.
60/829,148 filed on Oct. 12, 2006, is claimed; and which is herein
incorporated by reference.
[0002] This is related to U.S. patent application Ser. No. ______,
filed Jul. 9, 2007, as TNW Docket No. 2517-001 entitled
"Self-Contained Surface Physiological Monitor with Adhesive
Attachment"; United States patent application Ser. No. ______,
filed Jul. 9, 2007, as TNW Docket No. 2517-002 entitled "Single
Use, Self-Contained Surface Physiological Monitor"; which are
herein incorporated by reference.
BACKGROUND
[0004] 1. Field of the Invention
[0005] The present invention relates generally to a self-contained
device to monitor at least one physiological parameter of a
subject.
[0006] 2. Related Art
[0007] It can be difficult to monitor or diagnose medical or
physiological conditions of a patient away from a medical facility.
Often, medical equipment is tied to use in such a facility
requiring transport of the patient to the facility. In some
situations, special vehicles can transport some special equipment
to a patient. It will be appreciated, however, that situations can
be presented in which transportation of the patient may not be an
option, or in which immediate medical attention is required without
waiting for transportation, or when conventional monitoring
equipment cannot be supplied in sufficient quantities for the
numbers of patients requiring monitoring.
[0008] For example, it can be difficult to assess if unconscious or
semi-conscious patients are having nonconvulsive seizures,
especially in situations where nerve agents may have been used and
patients are experiencing extreme muscle fatigue and/or partial
paralysis. The ability to robustly and efficiently identify status
epilepticus (SE) in these patients can greatly assist emergency
medical personnel in determining initial treatment on site and
during transport to a medical facility where more comprehensive EEG
monitoring will be performed.
SUMMARY OF THE INVENTION
[0009] It has been recognized that it would be advantageous to
develop a device to monitor at least one physiological parameter of
a subject that is self-contained. In addition, it has been
recognized that it would be advantageous to develop a monitor
device to monitor at least one physiological parameter of a subject
that is single-use, or disposable. In addition, it has been
recognized that it would be advantageous to develop a monitor
device to monitor at least one physiological parameter of a subject
with a graphical display capable of displaying a physiological
variable value as an instantaneous value or as a trace showing the
evolution of the condition in time.
[0010] Furthermore, it has been recognized that it would be
advantageous to develop a self-contained epileptic seizure or
status epilepticus monitor device and method. In addition, it has
been recognized that it would be advantageous to develop a seizure
monitor device and method that is small, rugged, and able to be
used by first responders. In addition, it has been recognized that
it would be advantageous to develop a seizure monitor device and
method with the ability to simultaneously assess large numbers of
casualties at a site; that has a simple and fast application
procedure for each patient, even for first-response personnel who
are outfitted with emergency and/or protective gear; the ability to
easily continue monitoring the patient throughout stabilization and
relocation to a treatment facility; and the ability to keep the
devices in a compact case or field kit for emergencies (such as
storage life of 10 to 15 years from date of manufacture).
[0011] The invention provides a self-contained seizure monitor
device configured to monitor a subject for an electrographic
seizure. The device includes a pad with an adhesive layer
configured to adhere to a subject's skin. At least a pair of
electroencephalographic electrodes is carried by the pad and spaced
apart from one another. The electrodes are configured to sense
brain activity and generate a signal. A signal processing means is
carried by the pad and electrically coupled to the electrodes for
processing the signal. An indicator is carried by the pad and
electrically coupled to the signal processing means and configured
to indicate seizure information (such as the instantaneous index of
seizure or status epilepticus as well as its progression over
time). A power source is carried by the pad and electrically
coupled to the electrodes, the signal processing means, and the
indicator.
[0012] In addition, the invention provides a method for monitoring
a subject for an electrographic seizure, comprising:
[0013] adhering an adhesive layer carried by a pad of a
self-contained seizure monitor device on a head of a subject, and
thereby disposing an electroencephalographic electrode carried by
the pad against skin of the subject;
[0014] causing the monitor device to power from a power source
carried by the pad of the self-contained monitor device, and
causing the electrode to sense brain activity and generate a
signal, and causing an EEG signal processor carried by the pad and
electrically coupled to the electrode to process the signal;
and
[0015] viewing an indicator of seizure status carried by the pad
and electrically coupled to the signal processor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Additional features and advantages of the invention will be
apparent from the detailed description which follows, taken in
conjunction with the accompanying drawings, which together
illustrate, by way of example, features of the invention; and,
wherein:
[0017] FIG. 1 is a top perspective view of a self-contained monitor
device introducing several types of indicators used in several
embodiments of the present invention;
[0018] FIG. 2 is a schematic view of a self-contained monitor
device in accordance with an embodiment of the present invention
configured as a self-contained seizure monitor device displaying
the evolution of epileptiform electrographic activity and also
including pulse oximetry and heart rate monitoring;
[0019] FIG. 3 is a schematic view of the monitor device of FIG. 2
shown applied to a subject;
[0020] FIG. 4 is a top perspective view of an adhesive
physiological monitor device according to another embodiment;
[0021] FIG. 5 is a schematic view of a patient or a subject showing
possible locations for sensors of the device in FIG. 4;
[0022] FIG. 6 is a schematic view of the monitor device in FIG. 4
applied to a human subject;
[0023] FIG. 7 is a schematic circuit outline of the monitor device
of FIG. 4;
[0024] FIG. 8 is a bottom perspective view of the monitor device in
FIG. 4 shown with the release liner partially removed;
[0025] FIG. 9 is an exploded perspective view of the monitor device
of FIG. 4;
[0026] FIG. 10 is a top perspective view of another self-contained
monitor device in accordance with another embodiment including a
means to limit the device to a single use;
[0027] FIG. 11 is a bottom perspective view of the monitor device
in FIG. 10 with the release liner partially removed.
[0028] FIG. 12 is a schematic view of a monitor device including a
separate physiological sensor applied adhesively;
[0029] FIG. 13 is a schematic view of a monitor device including a
separate physiological clip-on sensor;
[0030] FIG. 14 is a schematic view of another self-contained
monitor device in accordance with another embodiment of the present
invention including both integrated and separate physiological
sensors;
[0031] FIG. 15 is a schematic view of another self-contained
monitor device in accordance with another embodiment of the present
invention comprising a reusable portion and a disposable
portion;
[0032] FIG. 16 is a schematic view of another self-contained
monitor device in accordance with another embodiment of the present
invention comprising multiple adhesive layers to enable multiple
use;
[0033] FIG. 17 is a schematic view of a treatment kit including the
self-contained monitor device;
[0034] FIG. 18 is a schematic view of a self-contained monitor
device in wireless communication with an external device such as a
hand-held computer;
[0035] FIG. 19 is a diagram showing the wireless system diagnostics
and upgrade;
[0036] FIG. 20 is a schematic view of a patient simulator in
accordance with an embodiment of the present invention.
[0037] Reference will now be made to the exemplary embodiments
illustrated, and specific language will be used herein to describe
the same. It will nevertheless be understood that no limitation of
the scope of the invention is thereby intended.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT(S)
[0038] As illustrated in FIGS. 1-12, various embodiments of a
self-contained monitor device, indicated generally at 10-10e, in
accordance with an exemplary implementation of the present
invention is shown to monitor at least one physiological parameter
of a subject 30 (FIG. 3), such as a human patient. The device can
monitor, and the physiological parameter can include, heart rate,
oxygen level, respiration rate, body temperature, cholesterol
level, blood glucose level, galvanic skin response,
electrophysiology, blood pressure, EEG, ECoG, EMG, ECG, ENG, skin
impedance, humidity, ultrasound absorption, light and infrared
absorption, acoustic or vibratory signals, movement, combinations
thereof, etc. Based on the physiological parameters measured, the
device can determine health status, determine degree of injury,
and/or detect the presence or lack of pathological conditions. In
an embodiment, the device also indicates the progression of a
physiological condition over time as a time series on a graphical
display 18. The self-contained device can be completely integrated,
topically applied, and disposed entirely on the subject.
[0039] In accordance with one aspect of the present invention, the
monitor device 10 can include a pad, patch, or housing 13 that
carries and/or contains various components of the device. The pad
can be flexible and capable of contouring to a subject's body.
Alternatively, the pad or housing can include rigid portions joined
by flexible portions that allow the rigid portions to pivot with
respect to one another to more closely contour to the subject's
body. The pad can be formed of a plurality of layers stacked
together to form the pad, as described in greater detail below. The
pad can have a substantially flat configuration in storage, and an
arcuate or deflected configuration in use. The various components
can be integrated into the pad so that the pad or device can be
topically applied and entirely disposed on the subject. The pad can
be sized and shaped to cover and/or extend between desired portions
of the subject's body. For example, the pad can have a length of
approximately 4-6 inches if applied to a subject's forehead.
[0040] An adhesive or adhesive layer 51 (FIGS. 8 and 9) can be
disposed on the device or pad to adhere the device or pad to a
subject's skin. For example, the pad and adhesive layer can include
single-sided or double-sided pressure sensitive adhesive foam. The
adhesive layer or foam can form one of the plurality of layers of
the pad. A release liner 52 (FIGS. 8 and 9) can be removably
disposed over the adhesive layer 51 before use or during storage to
protect and preserve the adhesive layer, and to resist unintended
adhesion. Alternatively, the pad can be applied to the subject's
skin by force, wrappings, suction, gravity, water tension, etc. The
adhesive layer 51 can be an integrated part of the pad that can
limit the device to a single use. For example, the adhesive layer
can be configured with sufficient adhesion for a single use, with
exposure to air and/or skin oil effectively prohibiting subsequent
use. Alternatively, the device can be configured for multiple uses
with the same or a different subject. For example, various
components of the device can be removable from the pad or adhesive
layer so that the same components can be used with another pad or
another adhesive layer.
[0041] One or more physiological sensors 12 can be carried by the
device or pad and configured to be applied to the subject's skin.
Thus, the adhesive layer 51 can surround the sensors 12 to maintain
contact between the skin and the sensors. In one aspect, one or
more apertures 54 (FIGS. 8 and 9) can be formed in the adhesive
layer 51 with the sensors 12 partially or wholly disposed within
the apertures. It will be appreciated that an electrically
conductive gel can be disposed over the sensors and protected by
the release liner 51 and/or an adhesive seal. In addition, a thin
film of sodium chloride can coat the sensors to draw moisture into
the electrode interfaces and thus improve contact through oily
skin.
[0042] The sensors 12 can be any type of sensor or electrode and
can be active or selectively active depending on the state of the
device and the type of analysis being performed. The sensors can
passively sense physiological signals, as in the case with EEG
electrodes, or can actively apply energy to the subject to sense
the signal or parameter, such as with electrical impedance
measurement or light absorption measurement for blood oxygenation.
Active sensing can also include applying visual, auditory,
somatosensory or electrical stimulation to record
electrophysiological measures such as nerve conduction velocity or
evoked responses such as ABER or P300 waveforms. The electrodes may
be made of Ag/AgCl packaged with an electrically conductive gel and
a special adhesive sealed cover to prevent the gel from drying out.
The electrodes may also be dry gold electrodes coated with a thin
film of sodium chloride to quickly draw moisture into the electrode
interfaces and improve contact through oily skin. The electrodes
may also be made of another electrically conductive material.
[0043] The sensors can sense or monitor one or more subject
physiological parameters and generate physiological signals. As
described above, the sensors can sense or monitor heart rate,
oxygen level, respiration rate, body temperature, cholesterol
level, blood glucose level, galvanic skin response,
electrophysiology, blood pressure, EEG, ECoG, EMG, ECG, ENG, skin
impedance, humidity, ultrasound absorption, light and infrared
absorption, acoustic or vibratory signals, movement, combinations
thereof, etc. The sensors can be configured to sense the same or
different physiological parameters, or different aspects of the
same physiological parameter.
[0044] As described above, the sensors can be integrated into the
pad or housing as one unit applied to the patient. Alternatively,
one or more sensors can extend from the main unit and be coupled to
the main unit by tabs or lead wires. Thus, the sensors can be
disposed on other parts of the subject away from the main unit
(FIGS. 12-14).
[0045] Signal processing unit or units 62 (FIGS. 9 and 10) or other
electronics, integrated circuits or signal processors can be
carried by or contained within the device or pad. The signal
processing units 62 can be coupled to the one or more physiological
sensors 12. The signal processing units 62 can process or analyze
the physiological signals received from the sensors and generate
other signals, such as display or indicator signals or alarms. The
signal processing units 62 and electrical connections can be
disposed on a circuit layer 61 such as a thin-film polyimide
(Kapton) circuit substrate that is flexible. This circuit layer may
contain all the necessary electronics in the patch. The circuit
layer may 61 can be disposed on top of the adhesive layer 51 or the
double-sided pressure sensitive adhesive foam.
[0046] The signal processing units 62 can analyze signals from the
sensors. Analysis can be performed by digitally processing the
signals in a computing device such as a microprocessor, DSP, FPGA,
or CPLD device, including any multiplexing and/or analog to digital
conversion that may be necessary for processing the signals in the
digital domain. Analysis may also be performed by applying analog
implementations of algorithms, computational techniques, or
detection methods, including linear and non-linear filtering,
rectification, summation, logarithm/exponential conversion,
thresholding, comparison, etc.
[0047] The integrated circuit and signal processor can also include
internal programs and settings. The programs and settings can be
reprogrammed, changed and/or updated by exchanging data with the
device through an electrical contact, inductive link, optical
and/or infrared link, RF data link, Bluetooth or other wired or
wireless method that can be applied for electronic communication.
The device can include error checking and/or correction schemes for
validating the data exchanged such as CRC, checksum, and other
known techniques, and/or include a variety of known authentication
methods for verifying the identity of the programmer and
authorization to change the device. Data exchanges with the system
can be performed with direct access to the system, through external
device packaging, through special windows or access ports within
packages, or through packages that include kits or other components
used with the system.
[0048] The signal processing units 62 can process or analyze
signals from the sensors 12, and can generate a physiological
result or value. The signal processing units 62 can generate a
display signal for a visual or audio indicator or a graphical
display. The physiological parameter or value can be heart rate,
oxygen level, respiration rate, body temperature, cholesterol
level, blood glucose level, galvanic skin response,
electrophysiology, blood pressure, EEG, ECoG, EMG, ECG, ENG, skin
impedance, humidity, ultrasound absorption, light and infrared
absorption, acoustic or vibratory signals, movement, combinations
thereof, etc.
[0049] In addition, the integrated circuit can generate a
physiological condition index based on at least one physiological
parameter. For example, the integrated circuit can generate an
epileptiform activity index or a status epilepticus index, such as
high, medium or low. The indicator or graphical display can display
the physiological condition index.
[0050] Furthermore, the signal processing units can generate an
alarm signal in response to a change of the physiological condition
index. The alarm signal can be send to an indicator, such as a LED
or graphical display, or to an audible device, such as a speaker or
buzzer.
[0051] In addition, the signal processing units can generate other
signals based on the operation of the device, such as power on,
battery level, sensors operable, etc. Furthermore, the integrated
circuit can generate user prompts or instruction signals for the
indicator, such as prompting the user to administer medication,
etc. The integrated circuit or signal processor is one example of a
signal processing means for processing the physiological signal or
for processing a signal from the at least one physiological
sensor.
[0052] One or more indicators, such as LED indicators 14, numeric
displays 16 or 16b, audible indicators 17 or speakers, or graphical
displays 18 can be carried by the device 10 and electrically
coupled to the signal processing units 62, such as by conductive
traces or lines on the circuit substrate. The indicator can include
one or more lights or LEDs 14, or can be numeric displays 16 such
as custom LCD, or can be graphical displays 18, such as LCD or
organic LED screens. Indicia can be disposed on the pad adjacent
the one or more lights or LEDs to indicate the condition of the
light or LED. The indicator 14, or the LEDs or LCD, can be carried
by the circuit substrate 61, and visible through a cover layer 66
(FIG. 9), or aperture 67 (FIG. 9) therein, as described in greater
detail below. The indicators 14, 16, 17, and 18 can indicate or
display information associated with the pad, the physiological
parameter, the subject, or combinations thereof. In addition, the
indicators 14 can also double as a switch or button, such as a push
button LED. Furthermore, the indicator can be a graphical display
capable of displaying graphical information, such as the
physiological value or its progression in time.
[0053] The indicator can also be, or can include, simple value
indicators, such as alphanumeric displays, bar meters, light
indicators with intensity or color modulation, and/or other
quantitative displays commonly used for electronic instruments,
such as LEDs, LCDs, electroluminescent, organic LEDs, mechanical
displays, cholesteric LCDs, electronic paper, etc. In addition, the
indicator can also be, or can include, auditory indicators, beeps,
alarms, quantitative indicators, such as auditory tones, beep
rates, etc, that change in tone and/or frequency, or even speech
signals that report information or give verbal prompts to users.
The indicator can also include indicators of the presence or lack
of specific subject or patient conditions or dangerous parameter
ranges by state indicators and/or binary true/false type indicators
that are either present or not. The indicator can also include
indicators of system status including battery level, power, sensor
conditions, analysis progress, or other information to update the
user on condition or state of the system. The indicator can also
include error signals used to instruct the user to correct the
application and/or use of the device or pad. The indicator can also
provide reliability or confidence level information for analyzed
data to assist the user in interpreting the results.
[0054] In situations where the system is used in kits that include
other components, such as devices or drugs, the displays may also
reference specific kit components or kit component labels, and/or
indicate the need to apply specific kit components based on
analysis performed. The kit can also contain detailed instructions
on how to administer the drugs.
[0055] A power source 40 (FIGS. 9 and 10), such as a battery, can
be carried by the device 10 or pad and electrically coupled to the
physiological sensors 12, the signal processing units 62 and the
indicators 14, 16, 17, or 18. The power source 40 or battery can be
carried by the circuit layer 61. In addition, the power source 40
can be sealed within the device 10 or pad so that the power source
is non-replaceable or non-removable.
[0056] The power source 40 can be, or can include, an integrated or
replaceable energy source such as a battery, fuel cell, capacitor,
dynamo, or other electromechanical system that derives electrical
power from stored mechanical energy such as a spring or pressure
tank. The device or power source can also receive power externally
from galvanic coupling to the skin, light and/or solar power,
chemical fuel, external inductive power, or mechanical movement
that is converted to electrical power for powering the device. The
device or power source can also contain an energy storage device
that uses the described external sources to charge and/or recharge
the device, for example, adding fuel to a fuel cell, charging an
integrated capacitor by inductive power, etc.
[0057] A cover 66 (FIG. 9) or cover layer can be disposed over the
circuit layer 61, the signal processing units 62, the indicators
14, 16, 18, the power source 40, or combinations thereof. The cover
can be formed of a polymeric material, such as an acrylic, and can
have an adhesive bottom to secure to the pad. In addition, the
cover 66 can include apertures 67 (FIG. 9) through which the
indicator 14, 16, 16b and/or 18 can extend or can be viewed, or
through which buttons or other input can extend or be accessed. The
cover can be substantially flat with raise portions to accommodate
the power source, integrated circuit, sensors, or combinations
thereof. The apertures 67 can be covered with a clear film to allow
viewing of the indicators while maintaining integrity to
moisture.
[0058] The device 10 or pad can be formed by the various layers,
such as the adhesive layer 51, the circuit layer 61 and the cover
layer 66. The layers can include adhesive or can be adhered
together. It will be appreciated that other forms of joining the
layers can be used, such as sonic welding, etc.
[0059] An exploded diagram of the general assembly concept for the
device is shown in FIG. 9. The core of the assembly is a very
flexible thin-film Kapton circuit assembly with top and bottom
copper layers. The electrodes are on the bottom of the substrate
and the electronics will be surface mounted on the top. The
top/bottom circuit layers also include actively driven shields over
the electrode areas to reduce electrical interference and motion
artifacts. The system can use dry gold electrodes for patient
contact. These can be coated with a thin film of sodium chloride to
quickly draw moisture into the electrode interfaces and improve
contact with the skin. Wet electrodes (using paste or gel)
currently dominate in clinical EEG applications as they have a
longer history of use and they can make better contact through
hair. However, controlled studies show that, when used with proper
electrical shielding, dry metal electrodes provide a more robust
connection that is more immune to electrical and movement artifact
(A. Searle and L. Kirkup, "A direct comparison of wet, dry and
insulating bioelectric recording electrodes", Physiol. Meas. 21
(2000) 271-283). In applications where motion artifacts are a
significant problem, a 3-axis accelerometer can be included in the
device for adaptive motion artifact cancellation.
[0060] The layers, or substrates forming the layers, can be
substantially flexible. For example, the pressure sensitive
adhesive foam of the adhesive layer, the polyimide (Kapton) circuit
substrate of the circuit layer, and the acrylic material of the
cover layer can be substantially flexible, and the combined adhered
layers can be substantially flexible. It will be appreciated that
the power source, integrated circuit and sensors can be rigid, and
can create rigid portions of the pad, while the spaces between the
rigid portions can be flexible portions about which the rigid
portions pivot. In addition, the pad 13 or housing can be sealed,
or one or more of the components can be sealed within the pad or
the housing. For example, the power source 40 or battery can be
sealed within the pad 13, or between the cover layer 66 and the
circuit layer 61 or between other layers to resist or prevent
removal of the power source. Resisting access to the battery can
limit the device to a single use, as described in greater detail
below.
[0061] The device can also include a button, switch or other
activator capable of activating the power source or the device for
use. For example, power can be enabled by a switch that is closed
or an energy barrier that is broken by the user activating a
control, removing a part, removing the device from packaging,
removing adhesive backings or strips, and/or applying the device to
the skin. For example, a tab 43 (FIGS. 9-11) can extend between the
power source 40 or battery, and an electrical connection, such as
on the circuit layer. The tab can physically block or prevent the
power source from electrically connecting to the circuit layer, or
the rest of the device. Removing the tab can allow the electrical
connection, and thus operation of the device. In addition, the tab
43 can be coupled to the release liner 52 and 52b (FIGS. 9-11) such
that removal of the release liner of the device also removes the
tab and enables operation of the device. The device can also
include low-power modes that allow it to operate without
significantly depleting the power source while in storage and
activate when used.
[0062] The device can include buttons or other controls that are
actuated to turn on/off the device, put the device in/out of
standby modes, initiate measurements, select modes or functions to
be performed, select types of analyses, change the types of
displays presented and/or their intensity or volume, clear alarms,
and/or otherwise change the function of the device. These controls
can include any type of control commonly used for electronic
devices, such as membrane switches, optical sensors, accelerometers
or movement sensors, capacitive switches, touch pads,
potentiometers, optical encoding dials, pressure sensors, etc.
[0063] The device 10 can also include data storage contained in or
electrically coupled to the signal processing units 62. The data
storage can be carried by the circuit layer 61. The data storage
can be used for recording subject signal data, analysis information
and results, user actions, and/or displayed information, along with
timing information, during operation. The data storage can include
any type and can be stored in any type of format. For example, the
data storage, or data storage means, can be, or can include, any
type of non-volatile memory system commonly used in modern
electronic devices including powered RAM, one-time-programmable
ROM, EPROM, EEPROM, or even consumer data storage devices such as
compact flash cards, SD cards, memory sticks, etc. The data storage
can include a means of encryption and/or secured access so that it
is only accessible by authorized users (eg, for HIPPA compliance),
including methods such as AES, Kerberos, or any other commonly used
encryption and authentication standards widely used in computer and
electronic devices. The data storage may also include error
detection and/or correction schemes for protecting data integrity.
The stored data may be accessed by wired connector or wireless
links similar to those described in the programming methods.
[0064] The device can also transmit data to and/or be controlled by
external systems, such as those used in monitoring systems in
emergency vehicles, central monitoring stations in hospitals,
mobile emergency response centers, or other situation where it may
be helpful or necessary to remotely monitor the parameters or
condition of one or more patients and/or the status of the
monitoring device. Thus, the device can include data transmission
means, such as an RF or IR transmitter 19, FIGS. 1, 7, and 18. Any
of a variety of wired or wireless low and high level data exchange
protocols commonly used for modern electronic communication can be
used for this purpose such as LVDS, RS232, USB, Ethernet, IrDA,
Bluetooth, Zigbee, 802.11, firewire, etc. The protocol can also
include authentication and data encryption to secure these
communications, such as AES, Kerberos, or any authentication and
data security scheme commonly used in modern electronic systems for
this purpose. Remotely activated controls may include any parameter
that can be accessed by the user as well as additional system
parameters and settings that can be only accessed by the remote
system. The remote system may also include the ability to override
user settings and/or transmit specific information to the device
for remote display to users of specific devices. The remote system
may also be capable of accessing recorded data in the system.
[0065] The device can also be capable of communicating its status,
programming, settings, battery conditions, identifying information,
etc, such as described above. The device can include unique
identifying serial numbers and other identifying device
characteristics that can be communicated as part of the programming
process and/or used for inventory, determination of component or
program compatibility, etc. Packages and kits that include the
device can also include separate identifying information, such as
ID numbers and codes, bar codes, RFID information, etc, that can be
used to determine and/or verify that the device and/or its settings
and programming are appropriate for the kit components.
[0066] As stated above, the device 10 can be configured as a
single-use device that is disposable after use. The device can have
various different configurations that limit the device to a single
use. As described above, the power source 40 can be sealed within
the pad or device 10 so that as the power source is depleted, the
device ceases to work. Thus, the power source 40 can include a
battery adapted to provide only enough power to complete a desired
task. Also as described above, the tab 43 can be coupled to the
release liner 52 and can extend between the power source and an
electrical connection. Thus, once the pad has been prepared for use
by removing the release liner, the power source is also engaged.
These are examples of means for limiting the device to a single
use. It will be appreciated that other means for limiting the
device to a single use can be used, including for example,
single-use adhesive for attaching the pad to the patient, or a
circuit element that disables the device following use.
[0067] The device can also include one or more means of movement
and location tracking, such as accelerometers and GPS, that are
recorded and registered with the patient and device data records.
These data may be used for review for general information purposes,
diagnostic analysis, post-mortem analysis of the system and its
functional history, and/or auditing of the history of subject
condition and external events during the use of the device.
[0068] The device can be used to monitor and analyze various
different physiological parameters and in various different
situations. Analysis can include determination of neurological
parameters and conditions, including health status, distress,
neural conduction velocity, muscle tone, depth of anesthesia,
alertness, level of consciousness, degree of neural injury,
seizures, status epilepticus, and/or non-convulsive epileptiform
activity, as well as activity indicative of imminent seizures or
other neurological episodes. Analysis can also include
identification of non-neurological parameters or conditions such as
heart rate, breathing rate, tachycardia, bradycardia, blood
oxygenation, hypoxia, etc.
[0069] The device can be used to monitor subject conditions, assist
in the determination treatments to be applied to a patients in a
clinical environment, and/or used in non-clinical monitoring
conditions such as personal health monitoring, alertness
monitoring, fitness and athletic performance monitoring, dietary
guidance, training and improvement monitoring, dangerous work
environments, etc.
[0070] For example, the device can be configured as a pulse
oximeter, or to include a pulse oximeter. Thus, the one or more
physiological sensors can include a photodiode emitter and sensor
for pulse oximetry. As another example, the device can be
configured to sense or monitor neural seizure or status
epilepticus. Thus, the one or more physiological sensors can
include a biopotential electrode.
[0071] The pads described herein are examples of means for mounting
the device on the subject, and/or for carrying the various
components. Other means for mounting include, for example,
adhesive, mechanical clip(s), mechanical compression bands, such as
armbands headbands, hair nets, etc. Thus, the entire device is
completely worn on the body.
Example 1
[0072] Referring to FIGS. 4-9, an exemplary embodiment of a
self-contained seizure monitor device 10c to monitor a subject for
an electrographic seizure is shown. Such a device can be used as a
field-deployable device that can be used to monitor status
epilepticus in casualties that may have been exposed to nerve
agents. The device is configured as a forehead patch for detecting
seizures, status epilepticus (SE), and/or other convulsive and
non-convulsive epileptiform activity in subjects that may have been
subjected to trauma or nerve or chemical agents. The patch
configuration can be very small relative to other commercially
available EEG systems, and rugged enough for robust use in field
environments. The device can be similar to that described above,
and the above description is herein incorporated by reference. The
sensors can be, or can include, at least a pair of
electroencephalographic electrodes, such as four electrodes 12,
carried by the pad and spaced apart from one another, and
configured to sense brain activity and generate a signal. The
device can include a battery 40, surface electrodes 12, EEG
acquisition and processing electronics 31, 32, and 33, and LED
indicators 14 The device can be activated by removing the adhesive
backing tab, and once applied, it can display seizure status for
several hours as the patient is stabilized and moved to a treatment
facility.
[0073] In one aspect, the device can be a small adhesive patch with
integrated EEG recording and signal analysis electronics 33 that
can be applied to the forehead. The patch can be activated by
removing the adhesive backing (and battery contact insulator tab)
and can display "OK" or "Seizure" status by small embedded LEDs
and/or audible alerts. EEG biopotential amplifier chip 31 (R. R.
Harrison and C. Charles, "A low-power, low-noise CMOS amplifier for
neural recording applications," IEEE J. Solid-State Circuits
38:958-965, June 2003) and low-power microcontroller technologies
have progressed to the point that this type of patch design is both
technically feasible and economical. In addition, with modern
lithium batteries, the devices can easily have shelf lives in the
range of 10 to 15 years.
[0074] The signal processing units can include a biopotential
amplifier 31 to acquire EEG signals. This amplifier can have a
CMOS-compatible bipolar-MOS "pseudo-resistor" to achieve
low-frequency response while using capacitively-coupled inputs to
reject large DC offsets. Amplifier bias currents can be selected
and transistors may be sized appropriately so that the input
differential pair transistors operate in the subthreshold region
(i.e. weak inversion) while the other transistors operate in the
traditional above-threshold region (i.e. strong inversion). By
operating the input devices in subthreshold, the
transconductance-to-current (gm/ID) ratio is maximized. This
results in an amplifier with a nearoptimum power-noise trade-off.
This amplifier has been used successfully for in vitro and in vivo
electrode recordings, and a low-power multiplexers (less than 5
.mu.W per channel) have also been added to the design and
experimentally validate (5.times.5 mm, 32-channel IC shown at
right). A complete discussion on the noise efficiency of the
amplifier and EEG optimization can be found in R. R. Harrison and
C. Charles, "A low-power, low-noise CMOS amplifier for neural
recording applications," IEEE J. Solid-State Circuits 38:958-965,
June 2003. This fully-integrated circuit requires no off-chip
components, and provides the size, power, .mu.V noise, and
bandwidth performance needed for the proposed EEG recording
system.
[0075] The device can include all the necessary electronics to
operate the device. The device can use a custom ASIC EEG amplifier
device and a TMS470 family microcontroller 33 for program storage
and data analysis. The 470 family has adequate computational power
for this application and can be changed to a higher power
microcontroller if necessary. The device can be battery powered
during operation for a minimum of four hours. At the end of the
program, an inductive link can be used, similar to an RFID reader
system capable of power-up and data transfer for functional
verification testing during manufacture and periodic field
inspection. This inductive link can also be used to add updated
software detection algorithms and updated care instructions to
utilize new, improved drugs for seizure treatment for the
integrated kits. The inductive link may also be used to transmit
patient data to an external receiver device (a phone, a computer, a
PDA, a digital audio player, or another type of external receiver)
to allow a single caregiver to assess the status of a large number
of patients simultaneously. The device can also have the capability
to log data indicating archived patient seizure status for the
duration of use. The logged data can be retrieved even after the
internal battery is discharged by using an inductive power signal
to activate the patch for data transfer. The electronics in the
device can also include a 3-axis accelerometer to be used for
adaptive motion artifact cancellation.
[0076] A simple user interface can be to provide "OK" vs. "Seizure"
LED indicators. In addition, if the devices are to be stored for
some time, the devices can have an initial indicator that the
device is electrically functional. Furthermore, the device can be
capable of communicating that the electrodes are in good contact
during use. The "good connection" indicator would also be helpful
as it may take a few seconds for the device to provide a reliable
indication, and in an emergency situation, the LEDs might never go
off as this may be interpreted as a device failure.
[0077] For example, the device can include four indicator LEDs 14,
including: Power, Connected/Analyzing, green "OK", and red
"Seizure". Although the interface could use fewer LEDs (eg, use
different colors for the same LEDs to denote different states), the
use of simple, single-state indicators can be unambiguous, more
reliable, and non-confusing for color-blind individuals ( 1/20th of
the general male population). Only one LED can be active at any one
time. Other alternatives are possible for user interfaces for this
device depending on how the device is packaged with drugs and other
emergency response components and the degree to which
classification of different ictal patterns is useful.
[0078] The device can have a seizure status indicator mounted on
the outside of the device. This indicator can reflect the result
the analysis of the seizure detection algorithm to the first
responder. It can include a series of LEDs illuminated above
descriptive text. A possible manifestation of this system may be a
series of four LEDs, one to indicate the patch is powered, another
to indicate sufficient electrode contact and data analysis, another
LED can indicate non-ictal activity, and the fourth can signal a
seizure. Only one light at a time can be turned on to simplify
interaction with the device. The patch may be configured such that
one light is always illuminated to avoid possible confusion. This
system of LEDs can also incorporate other LED to signal first
responders to administer certain drugs (e.g. two LEDs would
indicate the use of either Drug A or Drug B). There may be an
additional system to indicate the severity of the detected seizure.
The device may also have a miniature LCD screen on the front to
display a channel(s) of raw EEG data to allow trained users to more
closely monitor a patient. The indicator can also have a sound
signal.
[0079] For example, if the device is only used in first responder
kits with auto-injectors with different drug options depending on
early stage seizures vs. later stage SE EEG activity, it can be
beneficial for the device to have action-based indicators, such as:
Power, Patient OK, Inject Drug A, Inject Drug B, and Apply Patch
More Tightly. Alternatively, if feedback from the device will be
used with a more skilled technician who will also be weighing in
physical symptoms to determine treatment, the device can have
graded indicators of seizure activity, such as: Fasten Electrodes,
and Seizure Index: Low, Med, Hi.
[0080] In another embodiment, a full graphical display may be used
to indicate the current pathology status as well as its evolution
over time to assist in the assessment of the effectiveness of an
administered treatment, for example.
[0081] The device can include all necessary electrodes and
electronics to detect EEG signals, analyze EEG signals, and display
seizure status. The device can have different configurations
depending on the expected skin access of the subject. For example,
the device can have a two-electrode configuration, described above,
or 4 lead system with three differential views across the forehead
F8-Fp2, Fp2-Fp1, and Fp1-F7 (according to the international 10-20
electrode montage system) plus a central forehead reference/ground
electrode (e.g. Fz), or a six lead (plus ground/reference) system
which also adds electrodes that wrap around to A1 and A2 skin areas
located on or behind the ear. The device can be configured to place
the electrodes 30c-f on the scalp below the hairline. Electrodes
may be placed at the standard EEG recording locations including,
but not limited to Fp1, Fp2, F7, and F8, as shown in FIG. 8. The
device can also include electrode tabs applied to the back of the
neck or tabs electrodes designed to penetrate through the hair to
make contact with one or more scalp sites such as the apex of the
head. Electrodes can penetrate the hair by use of an electrolytic
gel or sharp contacts that penetrate and hold the skin of the
scalp.
[0082] The device can record brain signals from the series of
electroencephalographic (EEG) electrodes 12 attached to the scalp
outside the hairline. These EEG signals can be interpreted via a
small, integrated circuit embedded within the patch. The circuit
can analyze the data using specialized detection algorithms and
display the patient's seizure status on the front of the patch.
[0083] The device can include of a series of layers including a top
polymeric, such as acrylic, cover with a seizure status indicator
and device labeling. The bottom of this acrylic layer can have an
adhesive backing to attach it to the subsequent circuit layer. The
circuit layer can be made of a flexible, thin-film polyimide
(Kapton) circuit substrate. This circuit layer can include all the
necessary electronics in the patch. The circuit layer can be
disposed on top of a double-sided pressure sensitive adhesive foam
to hold the patch close to the skin. During storage this three
layered patch can have an adhesive cover over the foam layer to
protect the electrodes and isolate the battery to prevent the
device from powering up.
[0084] The device can use seizure detection algorithms to interpret
patient EEG data. Unlike other commercially available EEG
recorders, this device can selectively detect certain types of
seizures. In one aspect, the device can be used to detect ongoing
secondary generalized nonconvulsive seizures resulting from nerve
agent exposure. Initial seizures following nerve agent exposures
can be easy for non-physician first responders to diagnosis and
treat. The subsequent recurring seizure activity can be more
subtle, although it may still result in potentially dangerous
neural sequelae. This recurring seizure activity has been
identified as having similar electroencephalographic
characteristics to status epilepticus (SE). Thus, the seizure
detection algorithm can specifically detect SE in nerve agent
victims using a combination of threshold detection and spectral
decomposition elements to robustly detect seizure.
Example 2
[0085] Referring to FIGS. 2-3, another embodiment of a
self-contained electrographic activity monitor 10b is shown which
is similar in many respects to that described in Example 1 and the
above description is incorporated by reference. The device
integrates electrodes 12 to collect electrophysiological signals
and LED sensors (not shown) for pulse oximetry and heart rate
monitoring (sensors not shown). Such a device can be used as a
field-deployable device to monitor the development of status
epilepticus in casualties that may have been exposed to nerve
agents, for example. Other applications are possible, such as
neonatal epilepsy and SIDS (sudden infant death syndrome)
monitoring, for example. The analysis results are displayed as a
time series on a graphical display 18 to convey the effectiveness
of treatment, for example. The results of pulse oximetry and heart
rate monitoring are displayed on a numerical display 16b. A speaker
17 is included to indicate escalations of risk factors. The device
is applied adhesively. The patch 13b is capable of flexing and
conforming to the anatomy.
[0086] Seizure Detection Algorithms
[0087] Detection of seizure or ictal states from surface EEG
recordings is a complex subject with a large body of literature
spanning the last few decades (S. Faul, G. Boylan, S. Connolly, L.
Mamane, G. Lightbody, "An evaluation of automated neonatal seizure
detection methods," Clin. Neurophysiol. 116(7): 1533-41, 2005). Any
existing EEG seizure detection algorithm that can be integrated
into a compact, low-power microprocessor can be used with this
device. Most of the first generation circuits for seizure detection
were simple devices that looked for energy in certain frequency
bands beyond programmed thresholds (T. L. Babb, E. Mariani, P. H.
Crandall, "An electronic circuit for detection of EEG seizures
records with implanted electrodes," Electroencephalogr. Clin.
Neurophysiol. 37(3):305-8, 1974). These systems were effective at
detecting large seizures, but they had poor rejection of motion
artifacts and other noise sources that would cause false positives.
Modern algorithms developed over the last two decades generally use
a combination of spectral decomposition of the EEG signal, combined
with statistical metrics trained from seizure and non-seizure
recordings. Some also use abstract statistical measures of the
signal coherence and/or complexity.
[0088] The system can use the algorithm developed by Gotman (J.
Gotman, "Epileptic recognition of epileptic seizures in the EEG,"
Electronencephalogr. Clin. Neurophysiol. 54(5):530-40, 1982), and
the more recent algorithm by Saab and Gotman (M. E. Saab, J.
Gotman, "A system to detect the onset of epileptic seizures in
scalp EEG," Clin. Neurophysiol. 116(2):427-42, 2005), as well as
variations of the "Reveal" algorithm developed by Wilson et al (S.
B. Wilson, M. L. Scheuer, R. G. Emerson, A. J. Gabor, "Seizure
detection: evaluation of the Reveal algorithm," Clin. Neurophysiol.
115(10):2280-91, October 2004). The original algorithm by Gotman is
commonly regarded as a gold standard for evaluating other
algorithms and it is available in most EEG analysis packages. It
basically looks at the strength of prototypical features of ictal
activity compared to measures of the background activity. The
Reveal algorithm is a more modern spectral algorithm expected to be
more accurate for periodic discharges typical of ongoing status
epilepticus.
[0089] A field EEG system used to assess the chemical exposure
threat of nerve agent patients should be able to classify three
qualitatively distinct patterns of EEG activity including primary
generalized "grand mal" seizure activity accompanied by either
tonic-clonic behavior or flaccid paralysis, ongoing primarily and
secondarily generalized convulsive and nonconvulsive status
epilepticus, and normal post-ictal patterns which may be
accompanied by unrelated spastic muscle twitch.
[0090] In the case of primary generalized grand mal seizure type
activity a patient will likely present a number of other
pathological signs that can be interpreted by a non-clinician first
responder (e.g. tonic-clonic behavior) to prompt initial drug
treatment. However, patients may also exhibit flaccid paralysis
during this type of seizure event making it more difficult for the
non-physician to interpret. Designing an algorithm to detect
seizure activity from these signals will rely on spectral shift
analysis (predominance of 3 Hz activity), signal amplitude
increase, and an increase in synchronous activity across recording
channels. This type of seizure activity will be relatively easy to
detect from EEG recordings.
[0091] Status epilepticus (SE) EEG patterns are not as easily
discerned as primary generalized seizure activity. SE may present
as partial or generalized epileptiform activity. Treiman (D. M.
Treiman, "Generalized convulsive status epilepticus in the adult,"
Epilepsia, 34 Suppl 1:S2-11, 1993) describes a succession of
electrographic events which characterize SE starting with discrete
seizures with low voltage fast activity. As the seizure develops,
the low voltage activity spreads and gradually increases in
amplitude and decreases in frequency. Cerebral rhythms are then
obscured by the characteristic muscle artifact of tonic convulsive
activity, which is rhythmically interrupted as the patient converts
to clonic seizure activity. At this point, there is a gradual
increase in amplitude and decrease in frequency until the clonic
activity and its associated EEG discharged abruptly stop. Low
voltage slow activity is then seen. In nerve agent induced seizure
recorded in animals, this abrupt stop in high amplitude activity is
seen in experiments in which animals are treated with atropine. If
untreated this activity may persist for extended periods of time.
There may be a gradual evolution toward consciousness during this
interictal stage. However if the patient and EEG do not fully
recover before the next seizure occurs, the patient is considered
to be in generalized status epilepticus.
[0092] If secondary status epilepticus is allowed to persist
untreated or inadequately treated, the discrete electrographic
seizures begin to merge together so that there is a waxing and
waning of ictal discharges on the EEG. Waxing and waning of ictal
rhythms is characterized principally by a speeding up and slowing
down of the frequencies of the EEG, but there may be some amplitude
variability as well. As the discrete seizures merge together, the
record becomes fairly continuous. The continuous discharges are
then punctuated by periods of relative flattening that lengthen as
the ictal discharges shorten until, finally, the patient is left
with periodic epileptiform discharges on a relatively flat
background. This periodic ictal firing can present as either a
polyspike wave form or a simpler periodic epileptiform discharge
(PED). This polyspike activity is an example of generalized
convulsive SE in which patients may be either conscious or
comatose. This specific example of repetitive polyspike activity
was recorded from a comatose myoclonic SE patient. PED signals are
spikes that occur every 1 to 2 seconds. The complexes often consist
of sharp waves that may be followed by a slow wave. The question of
whether or no PEDs represent interictal or postictal activity
remains a topic of contemporary investigation. It has been claimed
(A. Krumholz, "Epidemiology and evidence for morbidity of
nonconvulsive status epilepticus," J. Clin. Neurophysiol,
16:314-23, 1999, E. Niedermeyer and M. Ribeiro, "Considerations of
nonconvulsive status epilepticus," Clin Electroencephalogr.
31:192-5, 2000) that these complexes do not reflect ongoing seizure
activity, instead they are a manifestation of damage from severe
brain injury. It has also been claimed that PEDs represent ictal
EEG discharges as these complexes can be eliminated with
antiepileptic drugs (D. M. Treiman, "Generalized convulsive status
epilepticus in the adult," Epilepsia, 34 Suppl 1:S2-11, 1993).
[0093] Nerve Agent Exposure and Device Use Profile
[0094] Newmark (J. Newmark, "Nerve Agents," Neurol Clin,
23:623-641, 2005) has provided several reviews of nerve agent
symptoms and casualty management. Several aspects of nerve agent
management have been identified that are important to this
application and not obvious from a uniquely EEG monitoring
perspective.
[0095] Nerve agent intoxication emergencies may unfold over the
course of several minutes to as long as an hour. Depending on the
methods of exposure, nerve agent symptoms may emerge quickly (e.g.,
inhalation or large skin contact areas) or surprisingly slowly. Of
particular concern are clothing and/or skin exposures where
contaminated clothes or fatty skin may act as reservoirs that
continually dose the patient for some time after exposure.
[0096] EEG may actually not be very useful for patients presenting
with flaccid paralysis. Patients that have systemically paralyzing
levels of exposure are usually severely affected by the exposure to
a degree that nerve agent symptoms are obvious, and circulatory and
breathing management will be the primary goals for first
responders. Patients presenting with these systems will quickly be
given anticonvulsive and antiagent drugs as part of their initial
treatment and EEG screening would not significantly improve patient
outcomes or alter care in these extreme cases.
[0097] Early treatment and seizure management significantly
improves patient outcomes. In exposure patients where the initial
encounter is non-lethal, it is important to monitor for the
emergence of continual seizure or status epilepticus (SE) brain
activity and aggressively treat this condition quickly to avoid CNS
damage and sequelae. Secondary Generalized SE in these patients
will usually progress to recruit the entire cortex and result in
patient death if left untreated.
[0098] Most patients with nerve agent intoxication and SE will not
be completely paralyzed. This will be the case in patients with
moderate levels of exposure and these patients will have outwardly
visible convulsive activity that will trigger the use of
anticonvulsive and anti-agent drugs in their treatment without the
need for EEG monitoring.
[0099] The device can be used to manage patients between initial
treatment and arrival at a treatment facility with more
sophisticated monitoring. Depending on exposure type, patients may
relapse into nonconvulsive or "subtle" SE and/or their fatigue may
prevent convulsive activity from being readily noticed by care
staff. However, recognition of SE in patients during this phase can
be critical for additional anticonvulsive treatments to be
administered and patients to have favorable outcomes. Once a
patient is at a treatment facility, they can be analyzed with
multi-lead EEG systems rather than forehead-only designs to provide
more complete monitoring.
[0100] The device can be optimized for SE and nerve agent related
seizures, as opposed to general clinical seizures. There are a
large number of algorithms reported for general seizure detection
and new ones are published every day claiming improved efficacy.
Most try to detect multiple types of clinically encountered
seizures and they are normally optimized for event detection during
long-term monitoring. However, the present device may not have time
to collect extensive background data prior to being presented with
ictal activity. As such, it can be optimized specifically for nerve
agent SE and post-treatment ictal activity and it can have
extensive validation with nerve agent exposure model data.
[0101] Treatment protocols for these patients and appropriate SE
detection algorithms are an area of active research and they will
continue to evolve over the next few decades. Because of this, the
device can be field upgradeable to continually improve the standard
of care and protect device investments for emergency response
agencies. The device can also be used in or in conjunction with
treatment and casualty response kits. For example, for the
particular drug injectors and algorithms used in these treatment
packs, the device can be biased toward false positives or false
negatives, or the labeling and indicators on the device can refer
to specific user actions for the kit rather than labels for patient
diagnosis.
[0102] Civilian nerve agent emergency scenes can differ from
military scenes. In most civilian casualty scenes, the entire head
will be accessible. As such, the device can utilize skin areas
around the ears to get recordings of the temporal areas for
improved cortical coverage. In addition, as a general heuristic,
increasing the number of recording sites can improve the
performance and robustness of seizure detection algorithms. In most
civilian casualty scenes, the first responders will generally be
other civilians with limited training who are using emergency
response kits. As such, the kit and the EEG device can be highly
algorithmic with labeling and indicators. Tradeoffs between higher
sensitivity and false positives can be optimized for the specific
drugs in the kit and their side effects and the expected time to be
transported to a medical facility with more comprehensive EEG
monitoring.
[0103] Amplifier ASIC
[0104] For the electrophysiological signal acquisition system to be
very tightly integrated, ASIC biopotential amplifiers can be used.
One such amplifier has been developed by Prof. Reid Harrison in the
University of Utah, Department of Electrical Engineering (R. R.
Harrison and C. Charles, "A low-power, low-noise CMOS amplifier for
neural recording applications," IEEE J. Solid-State Circuits
38:958-965, June 2003) This basic design has been extensively
tested in animal neurophysiology experiments over the last six
years, and commercial versions of the design are now being
developed by Intan Technologies, LLC of Salt Lake City, Utah.
[0105] A CMOS-compatible bipolar-MOS "pseudoresistor" (Ma-Md) is
used to achieve low-frequency response while using
capacitively-coupled inputs to reject large DC offsets. Amplifier
bias currents Ibias are selected and transistors M1-M10 are sized
appropriately so that the input differential pair transistors
operate in the subthreshold region (i.e. weak inversion) while the
other transistors operate in the traditional above-threshold region
(i.e. strong inversion). By operating the input devices in
subthreshold, the transconductance-to-current (gm/ID) ratio is
maximized. This results in an amplifier with a near-optimum
power-noise trade-off.
[0106] This amplifier has been used successfully for in vitro and
in vivo electrode recordings, and a low-power multiplexers (less
than 50 .mu.W per channel) have also been added to the design and
experimentally validate (5.times.5 mm, 32-channel IC shown at
right). A complete discussion on the noise efficiency of the
amplifier and EEG optimization can be found in (R. R. Harrison and
C. Charles, "A low-power, low-noise CMOS amplifier for neural
recording applications," IEEE J. Solid-State Circuits 38:958-965,
June 2003). This fully-integrated circuit requires no off-chip
components, and provides the size, power, .mu.V noise, and
bandwidth performance needed for the proposed EEG recording
system.
[0107] Configuration Variations
[0108] Referring to FIGS. 10 and 11, a simplified device 10d is
shown that is similar in many respects to those described above and
the above description is incorporated herein by reference.
[0109] Referring to FIGS. 12-16, several other embodiments of a
self-contained physiologic monitor are shown schematically. In FIG.
12, the monitor device 10e includes a sensor 12d enclosed in
separate patch 92. The main unit 91 of the device is applied (by
adhesion, for example) to the patient for convenient viewing by
medical personnel and the sensor unit 92 is applied to an area that
is optimal for physiological signal acquisition. In FIG. 13, the
monitor device 10f is similar to 10e, the sensor unit 101 carrying
the physiologic sensor 12e constitutes a clip. Alternatively,
sensors may be integrated in an elastic head cap or a compressive
or elastic headband.
[0110] Referring to FIG. 14, the monitor device 10g is shown
including multiple separate sensor units 92a as well as a separate
sensor unit 92b containing multiple physiologic sensors 12f.
[0111] In FIG. 15, a partially reusable self-contained monitor
device 10h is shown comprising a reusable portion 122 and an
adhesive disposable portion 121. The disposable portion may contain
disposable sensors 12g and openings 125 for sensors 12h disposed on
the reusable unit 122.
[0112] In FIG. 16, a monitor device 10i with multiple adhesive
layers 131 is shown to allow multiple applications of the monitor
device.
[0113] Kits and Service
[0114] Referring to FIG. 17, the monitoring device 10 can be
integrated into a complete kit 140 for non-physician first
responders to use during initial treatment and transport of head
trauma, brain attack, nerve agent exposure patients, or patients
with other conditions to a treatment facility. The device 10 can be
battery-powered and the field-deployable kit 140 can include:
self-contained monitoring devices 10, treatment medication(s) 141,
instruction guides, and other components. For example, the kit can
include anticonvulsant and anti-cholinergic medications loaded into
autoinjectors, instructions for patch use, patch indicator
interpretation, and drug delivery instructions. This kit can allow
an untrained person to monitor a nerve agent exposure patient for
recurring ictal activity, and to treat any seizures that may occur.
The patch can internally detect the presence and severity of
seizure activity, and relay that information to the first
responder. The patch can indicate which medication at a given
dosage to administer to the patient based on recorded EEG signals.
The kit can also include some electronics to inductively power the
patches in order to assess remaining battery life, patch serial
number, and patch operation status. This inductive link can also
use low frequency power carrier modulation to send data to the
device and reflect impedance telemetry to signal data back out to
the programming pad 162 (FIG. 12).
[0115] Referring to FIG. 18, the monitor device 10 may establish a
wireless communication with an external device such as hand-held
computer 151 to upload analysis results, for example. This
mechanism may be used to ensure continuity of monitoring upon
transferring patients to a hospital, for example.
[0116] Referring to FIG. 19, in order to keep devices in the field
properly inspected and maintained, a programming pad 162 can be
used to inductively power the patch devices and query their
functional status, including current battery levels. The
programming pad 162 can be a standard Class-E transmitter design
with low-frequency power carrier modulation to send data to the
patch device and reflected impedance telemetry to signal data back
out to the programming pad (similar to the method used by RFID
devices used for consumer products and library books). This
inductive coupling mode can allow devices to be inspected
individually or within packaged kits. The inductive powering can
also be used to trickle-charge the batteries for further extending
shelf life.
[0117] The device may be powered by a number of different sources.
An inductive coil may be placed in the storage kit to maintain
charge while the patch is in storage. The device will remain
charged so long as it remains in the kit, and maintain its charge
for a limited duration (e.g. 4 hours) after being removed from the
kit and put to use. The device can have a medical-grade single-use
battery, which may be replaceable. The device may be able to
transmit battery configuration information such as number of charge
cycles, charge level, expected lifetime, etc. Batteries may include
overcharge control means.
[0118] Referring to FIG. 20, in order to characterize and test the
signal analysis systems, an additional system can be used to
present simulated signals to the signal analysis device. For
example, for EEG systems, scaled EEG recordings are presented onto
a rubber head model 170 for device verification testing. The system
can be validated by a patient simulator device 171 which transmits
physiologically relevant sample EEG data to an attached patch. This
patient simulator device would be made out of rubber or some other
moldable nonconductive material to match the same shape as a human
head. This mold would contain signal transmitters to emulate EEG
signals as they might be recorded from human subjects. The emulator
can include a PC connected to an analog output card and a resistor
scaling network. A saved data file of archived seizure EEGs can be
transmitted via this system to test the ability of the patch to
detect seizure and to rapidly evaluate seizure detection algorithms
without needing to use human subjects. The transmitted data can be
scaled down and mixed with artifactual movement related noise to
match physiological conditions.
[0119] While the forgoing examples are illustrative of the
principles of the present invention in one or more particular
applications, it will be apparent to those of ordinary skill in the
art that numerous modifications in form, usage and details of
implementation can be made without the exercise of inventive
faculty, and without departing from the principles and concepts of
the invention. Accordingly, it is not intended that the invention
be limited, except as by the claims set forth below.
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